To improve peelability of a cellulose acylate film from a substrate and to prevent contamination of production equipment caused by a release agent.

A dope that is brought into contact with a substrate and cast is mixed with a peel force adjuster. The peel force adjuster is a polyfunctional carboxylic acid derivative and has the weight ratio of the polyfunctional carboxylic acid in the polyfunctional carboxylic acid derivative to the polyfunctional carboxylic acid derivativef ≤1:1. The peel force of the cellulose acylate film 121 to be continuously peeled from a substrate 88 is ≤60×9.8 (mN) based on 1cm width. The cellulose acylate film 121 is quickly and stably released from the substrate, the occurrence of a metal salt of the peel force adjuster is controlled and contamination of film production equipment is prevented by the method. Consequently, a film having excellent optical characteristics is continuously produced at a high speed for a long period of time.